The employment of emulsion polymers for a wide variety of uses, including as coatings, adhesives, binders for fabrics, fibers and the like, is widespread in industry. In the past, polymers such as acrylates, methacrylates, vinyls and the like were typically employed in the form of solutions in various organic solvents. However, because of both cost and environmental considerations, there has been a continuing trend to replace such organic solvents with water with the resultant formation of aqueous dispersions.
This conversion from the use of organic solutions to aqueous emulsions, while beneficial from many standpoints, has nevertheless resulted in the creation of formulation problems. Specifically, unlike organic-based compositions which are, in general, true solutions, such aqueous-based compositions are dispersions which, without the presence of an effective stabilization agent, will settle out or coagulate upon storage, or under the high shear conditions associated with many application methods. Accordingly, there have been several attempts to provide compounds which will provide desirable storage stability to such aqueous polymer emulsions.
One class of compounds which has been used to afford stability to such emulsion polymer latices are high molecular weight water soluble compounds which are classified as protective colloids. Specific examples of such water soluble protective colloids include polyvinyl alcohols of various molecular weights and degree of hydrolysis, and cellulose derivatives such as hydroxyethylcellulose. These protective colloids are further described in publications, such as, for example, Hercules, Inc. bulletin YC-4506 and in "Water Soluble Polymers: Beauty With Performance," J. E. Glass, Ed., Advances in Chemistry Series 213, ACS (1986).
European Patent Publication 325,054 dated July 26, 1989 discloses a class of dispersion-stabilizing compositions which are the reaction products of (1) a compound containing a poly(oxyalkylene) group and having at least two -OH groups; (2) a compound other than as defined in (1) which contains at least two reactive hydrogen atoms present as -OH, -NH.sub.2 or -NHR; (3) a carboxylic acid containing at least two carboxylic acid groups or an anhydride or chloride thereof; and (4) a mono-carboxylic acid, a mono-hydroxycompound, a secondary mono-amine or a hindered primary mono-amine. These non-ionic compositions are described as being useful in the preparation of a wide range of emulsions or dispersions of solids and liquids.
Although both these classes of compounds have been individually found to greatly enhance the stability of emulsion polymer latices, it would nevertheless be desirable to possess dispersant compositions which yield additionally enhanced stability to such latex formulations as well as which provide improvement in polymerization parameters.
Accordingly, it is an object of this invention to provide a polymer latex composition exhibiting enhanced stability.
It is a further object of this invention to provide a polymer latex composition exhibiting reduced coagulation formation during the polymerization process.
It is yet a further object of this invention to provide a method for the production of a stable emulsion polymer latex with reduced coagulation formation.
These objects and other additional objects will become more fully apparent from the following description and accompanying Examples.